When coupling electro-optical transmitters, such as LEDs and laser diodes, and electro-optical receivers, such as photodiodes and phototransistors, by means of a light-conducting fibre, or when optically connecting two separate optical waveguides (e.g. of plastics material) to one another, the problem arises that the end faces of the light-conducting fibres have to be brought into position with respect to the corresponding transmitting or receiving faces very precisely and held there. In so doing, the optical axes have to be brought into congruence precisely and adjoin one another very closely, that is to say that they have to be positioned precisely both in the radial and in the axial directions.